Method for welding profiled elements in plastic material, in particular pvc

ABSTRACT

A method for welding profiled elements in plastic material includes: preparing two profiled elements, arranged with respective weld zones facing one another; making a groove corresponding to at least one weld zone of the profiled elements, the grooving performed by a removal operation on a peripheral edge of at least one profiled element; heating the weld zones; coupling the zones to be welded to one another, pressing the profiled elements together to keep the zones to be welded in reciprocal contact. The coupling step includes: a sub-step of melting the zones to be welded into one another in order to define a welding bead; a sub-step of making a containing compartment defined by the groove, the welding bead being made internally of the containing compartment; and the step of arranging a containing presser in correspondence to the containing compartment for preventing exit of the welding bead from the compartment itself.

TECHNICAL FIELD

The present invention relates to a method for welding profiled elementsin plastic material, in particular PVC.

BACKGROUND ART

In the state of the art, the PVC profiled elements, mainly used aswindow and door frames, are welded together by means of the melting ofrespective head surfaces in order to make a frame structure fittable todoors or windows.

In particular, the melting is done by heating the portions to beconnected using suitable electric heating plates and then pressing theheated portions the one against the other to favor melting.

Generally, the heated portions are the head extremities of the profiledelements, suitably cut at 45° to define e.g. a right-angled portion of arespective window or door frame.

This method is carried out by welding machines equipped with respectiveretaining members of the profiled elements, mobile in a reciprocalcloser moving direction to bring the heated extremities to be weldedinto contact.

Such machines are also equipped with finishing systems, suitable forremoving the bead or welding bead which forms during the melting of thetwo profiled elements.

In fact, in correspondence to the joining line of the two profiledelements (surfaces cut at 45°), the portion of melted material in excesscomes out and goes to form a bead protruding from the visible surface ofthe profiled elements. For this reason, in order to give the finisheddoor or window frame an appreciable aesthetic appearance, once weldedthe profiled elements undergo a bead removal operation.

The known welding devices briefly described do however have majordrawbacks mainly tied to the formation of the above-mentioned weldingbead.

It must in fact be considered that the welding zone of the PVC profiledelements is not perfectly uniform and consequently, to make the profiledelements even, a lot of material is melted with the consequent formationof an abundant bead, and there is consequently a lot of waste materialto be removed.

Furthermore, the finishing jobs for removing the bead and cleaning thewelding zone have a strong effect on the total time required to machinethe door or window frame. It should be realized in fact that for everydoor or window frame welding operation, the profiled elements have to besubsequently machined. Furthermore, in the case of spoked profiledelements, the removal of said bead is very complicated.

Furthermore, the machinery used for the above-mentioned finishingoperations is cumbersome and particularly expensive.

This results in the need to sustain additional costs and work timesbecause of the presence of further cumbersome equipment and tools.

DESCRIPTION OF THE INVENTION

In this context, the technical aim underlying the present invention isto propose a method for welding profiled elements in plastic material,in particular PVC, which overcomes the drawbacks of the above-mentionedstate of the art.

In particular, the object of the present invention is to place atdisposal a method for welding two profiled elements made in plasticmaterial, in particular PVC able to eliminate all subsequent additionaloperations suitable for removing the welding bead.

Another object of the present invention is to envisage a method forwelding profiled elements in plastic material, in particular PVC, thatis fast, cheap and with reduced space.

The above objects are achieved by a method for welding profiled elementsin plastic material, in particular PVC, comprising the technicalspecifications stated in any of the enclosed claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention willbecome more evident from the approximate but non-limitative descriptionof several preferred, but not sole, embodiments of a method for weldingprofiled elements in plastic material, in particular PVC, illustrated inthe annexed drawings in which:

FIGS. 1a and 1b show perspective and schematized views of a one-headdevice (the heads can be repeated on machines which work 4-6 cornerssimultaneoulsy) for welding profiled elements in plastic material, inparticular PVC, according to the present invention;

FIGS. 2a, 2b, 2c show details of the device in figures 1a and 1b inrespective operating conditions;

FIG. 3 show a detailed view of a further operating sequence;

FIGS. 4 and 5 show PVC profiled elements during the steps of reciprocalmoving closer;

FIGS. 6a and 6b show schematically two subsequent steps of thetraditional welding of the head extremities of the profiled elements, inparticular the compression step wherein the formation of beads on bothsides is highlighted: internal and external;

FIGS. 7a and 7b show schematically two subsequent steps of the weldingof the head extremities of the profiled elements according to theinvention wherein the formation of beads is highlighted only on theinternal sides of the profiled elements, i.e. on the sides delimitingthe internal space of the profiled element;

FIGS. 8a, 8b and 8c show schematically three subsequent steps of thewelding of the head extremities of the profiled elements according tothe invention wherein the formation and containing of beads ishighlighted inside a compartment obtained underneath the surface inorder to obtain the visibile external side not melted;

FIGS. 9a, 9b, 9c and 9d show schematically four subsequent steps of thewelding of the head extremities of the profiled elements according tothe invention wherein the formation of a containing barrier ishighlighted defined by a receding corner moving closer to a reliefcorner and which determines the formation of beads on the internal sidesonly of the profiled elements, i.e. on the sides delimiting the internalspace of the profiled element;

FIGS. 10a and 10b show, in a front view, the hot-plate heat-sealingelement in FIG. 9b in two different operating positions;

FIG. 11 is an axonometric view of an alternative embodiment of thedevice according to the invention;

FIG. 12 is an axonometric view, from another angle, of the device inFIG. 11;

FIG. 13 is a perspective view, on enlarged scale, of a detail of thedevice in FIG. 11;

FIG. 14 is an axonometric view, on enlarged scale, of a detail of theprofiled elements before welding;

figures from 15 to 17 show, in a succession of plan views, the operationof the device in FIG. 11;

FIG. 18 is an axonometric view, on enlarged scale, of a detail of theprofiled elements after welding obtained by means of the device in FIG.11.

EMBODIMENTS OF THE INVENTION

With particular reference to figures from la to 3, indicated by 1 is adevice for welding profiled elements in plastic material, in particularPVC.

Such device implements a method, or procedure, for welding profiledelements in plastic material, in particular PVC, wherein are arranged atleast two profiled elements 3, with respective zones to be welded 4facing one another.

The plastic material from which the profiled elements 3 are made is,e.g., PVC, but plastic materials of the heat-sealable type other thanPVC cannot be ruled out.

As will be better specified below according to the method, before thestep of heating and welding the profiled elements 3, a groove 19 is madein correspondence to at least one zone to be welded 4 of the profiledelements 3 by means of a removal operation (milling, melting,chamfering, etc.).

Subsequently, the zones to be welded 4 are heated and coupled, orjoined, by pressing the profiled elements 3 one against the other tokeep the zones 4 in reciprocal contact.

This way, the groove 19 or the grooves 19 of the two profiled elements 3define a containing compartment 19 a for containing a bead or weldingbead produced during the melting of the respective profiled elements 3.

In the rest of the present description, a single welding device 1 willbe illustrated suitable for welding the extremities of the tworespective profiled elements.

Nevertheless, the present invention can comprise a series of devices 1,each of which operating on a respective extremity of a profiled element3. For example, to make a rectangular frame to be used as a door orwindow frame, four devices 1 are used, each intended to weld theprofiled elements 3 in correspondence to right angles of the mentionedframe.

With reference to FIG. 1 it should be noted that the device 1 comprisesa base frame 38 that supports a pair of retaining members 2 ofrespective profiled elements 3 in PVC, suitable for engaging theprofiled elements 3 themselves with corresponding zones to be welded 4facing one another.

In particular, each retaining member comprises a base portion 5 on whichthe profiled element 3 is positioned, and a mobile portion 6 arrangedabove the base portion 5. The mobile portion 6 is suitably moved toshift towards the base portion 5 and thus retain the profiled element 3.

As can be seen on the attached illustrations, each profiled element 3 istherefore arranged between the base portion 5 and the mobile portion 6,with the respective head extremity protruding. The head extremities ofthe profiled elements make up the zones to be welded 4 and for thisreason they are facing one another.

It should also be noted that the zones to be welded 4 are suitably cutat 45° to define a coupling between two right-angled profiled elements.

Moreover, the device 1 comprises movement means 7 of the retainingmembers 2, to shift the profiled elements 3 between a first reciprocalaway direction and a second reciprocal closer direction wherein thezones to be welded 4 are coupled together.

In particular, for each retaining member 2, the movement means 7 have asliding guide 8, extending parallel to the longitudinal extension of theprofiled element 3. On the sliding guide is fitted a carriage 9 integralwith the aforementioned base portion 5.

Furthermore, each carriage 9 is coupled with a movement system 10 (notdescribed in detail because of known type and not forming a part of thepresent invention) suitable for moving both the carriages 9 of theretaining members 2 reciprocally closer/away.

The device 1 also comprises heating means 11 for heating theaforementioned zones to be welded 4 of the profiled elements 3 in PVC.The heating means 11 are preferably mobile between an active conditionwherein they are placed between the profiled elements 3, and a non-usecondition wherein they are spaced at a distance from the profiledelements 3.

In particular, it should be noted that when the profiled elements 3 arearranged by the movement means 7 in reciprocal away direction, theydefine a transit zone of the heating means 11. This way, once the zonesto be welded 4 have been heated, the profiled elements 3 are movedcloser together and pressed with the respective extremity heads againstone another.

Advantageously, the heating means 11 comprise a hot-plate heat-sealingelement 12, made up e.g. of a substantially plate-shaped electricresistance 12, fitted on a movement system 13. Preferably, the movementsystem 13 is composed of a pair of carriages 14 mounted sliding inrespective rails 15 and each of which arranged on opposite sides of theaforementioned resistance 12. This way, the resistance 12 is fastened tothe carriages 14 and moved by these along the rails 15. The carriages 14are also operatively connected to a motor 16, by means of a connectingrod-crank 17.

Advantageously, the connecting rod-crank 17 transforms the rotary motiongiven by the motor 16 into a back and forth motion of the carriages 14and of the resistance 12 to insert/remove the resistance 12 between/fromthe above-mentioned profiled elements 3.

The device 1 is also equipped with removal means 18 to make at least onegroove 19 on the peripheral edge of at least one zone to be welded 4.

The removal means 18, e.g., are composed of means of removal by milling;alternative embodiments cannot however be ruled out wherein the removalmeans are of a different type and envisage, e.g., one or more hotpoints, which remove the plastic material by melting, or one or moreultrasonic points.

The removal means 18 by milling comprise a supporting frame 20 placedabove the retaining members 2, and at least one machining tool 21 (acutter), facing a profiled element 3 to make the above-mentioned groove19 on the zone to be welded 4.

The tool 21 is moved by a motor part 22 preferably of the electric typeand miniaturized, brushless sensorless with very high rotation speed.

Furthermore, the tool 21 is moved by a movement member 23, between afirst idle condition (position in which it is placed between theprofiled elements 3) and a second working condition in which it isplaced between the profiled elements 3 in PVC.

In greater detail, the removal means 18 by milling preferably comprise apair of machining tools 21, each of which equipped with an active head21 a on the peripheral edge of a respective zone to be welded 4.

As illustrated in the detail views, the tools 21 are opposite oneanother to work at the same time on both the profiled elements 3.

Furthermore, the frame 20 has a supporting bar 24 arranged above theretaining members 2 and designed to sustain the tools 21 which in thissituation are mounted on a lower extremity of the bar 24 itself.

The bar 24 is operatively connected to the movement member 23 to bemoved in correspondence to the zones to be welded 4.

Advantageously, the tools 21 are positioned in correspondence to theside edge of the zone 4 by means of the movement of the above-mentionedmovement member 23.

In particular, the member 23 comprises a pair of supporting guides 25 onwhich the bar 24 is mounted sliding and moved by a known motor notdescribed in detail.

Furthermore, the bar 24 is moved vertically by means of an axis withwormscrew 26 arranged in correspondence to the supporting frame 20.

Advantageously, both the tools 21 and the motor part 22 are supported bythe bar 24 and are mobile with it both horizontally (along the guides25) and vertically (by means of the wormscrew 26).

The movement of the bar 24 is by means of a controlled-axis system whichenables the tools 21 to shift along the peripheral edge of the profiledelements 3 to obtain the grooves 19.

Thanks to the controlled-axis system, furthermore, the tools 21 aremoved between an idle position, wherein they are not placed between theprofiled elements 3, and a working position, wherein they are placedbetween the profiled elements 3.

The device 1 is also equipped with a containing presser 27 mobile alonga direction transversal both to the direction of movement of theprofiled elements 3 and to the lying plane on which they lie, to abut onthe grooves 19 made in the respective zones to be welded. Such pressercan be heated to better shape the plastic material underneath and canhave protrusions or recesses to reproduce a special shape on the hotpiece just machined. The still hot material is in fact easy to shape.

In particular, in the welding condition of the zones 4, i.e., when theyare brought into contact and pressed with each other, the grooves 19define a containing compartment 19 a in reciprocal collaboration.

Depending on the shape of the grooves 19, the compartment 19 a can beopen or closed, as will be better described below.

In the event of the compartment 19 a being open, it can be delimited bythe containing presser 27 which prevents the melted material coming outof the compartment 19 a.

Preferably, two containing pressers 27 are prepared, each of whichassociable with a respective pair of opposite grooves 19 to define twocontaining compartments 19 a for respective welding beads.

In particular, a first presser 27 is arranged above the profiledelements 3, while a second presser 27 is arranged underneath theprofiled elements 3.

It will in fact be noted that the grooves 19 are applied for theexternally visible portions of the profiled elements 3, i.e., the sideedges cut at 45° which when welded together determine the formation of aprotruding welding bead.

In this situation, the bead does not come out of the compartment 19 abut is contained inside it.

In this context, the pressers 27 are mobile by means of suitablemovement elements not described in detail and able to move closerto/away from the pressers 27 themselves during the various welding stepsof the profiled elements 3.

The device 1 is furthermore equipped with an electrostatic part 28 forretaining the shavings that form during the removal operation bymilling.

The electrostatic part 28 is made up of an electrode connected to thework tool 21 and connected to a high-voltage generator. This way, theshavings charged with negative polarity are retained by the head 21 a ofthe cutter (which acts as an electrode) charged positively to avoid thedispersion of the mentioned shavings.

In collaboration with or alternatively to the electrostatic part 28, thedevice 1 has a vortex suction system 29 a, 29 b concentric with the tool21 which permits removing the shavings which form during the removaloperation by milling.

The suction system 29 a, 29 b, e.g., consists in a chamber 29 a which isarranged around each tool 21 and which is connected to a suction duct 29b which moves the shavings away.

For this purpose, furthermore, the tool 21 consists of a helical-shapedcutter that conveys the removed shavings towards the inside of thechamber 29 a to make suctioning the shavings easier.

Advantageously, all the PVC shavings produced by the removal operationsby milling are easily suctioned.

The device 1 described above in prevalently structural terms implementsa welding method which is also the subject of the present invention.

The method comprises the steps of preparing at least two profiledelements 3, arranged with the respective zones to be welded 4 facing oneanother, in correspondence to the retaining members.

Then, the grooves 19 are made in correspondence to each zone to bewelded 4 of the profiled elements 3. The zones to be welded 4 aresubsequently heated and coupled together by pressing the profiledelements 3 one against the other. This way the zones 4 are kept inreciprocal contact to melt the zones 4 together thus defining thewelding bead.

In this respect, the fact is underlined that the step of making thegrooves 19 also comprises leveling the parts of the zones to be welded 4not occupied by the grooves 19.

In practice, the tools 21 are made to pass over the substantial totalityof the zones to be welded 4 at different work depths:

-   -   in correspondence to the peripheral edges of the profiled        elements 3, the work depth of the tools 21 is greater and such        as to define the grooves 19;    -   in correspondence to the remaining parts of the zones to be        welded 4, instead, the work depth of the tools 21 is less and        such as to only remove a small layer of plastic material, enough        to flatten and even out the zones 4 to be welded.

In other words, the purpose of the tools 21 is not only to shape thegrooves 19 but these are also fundamental for evening out the walls andcorrecting any cutting errors.

In the absence of such leveling, the zones to be welded 4 would be tooirregular and therefore not weldable.

It is also underlined that the grooves 19 and the leveling of the zonesto be welded 4 are made by the tools 21 of the device 1 when theprofiled elements 3 are already mounted on the retaining members 2 andthe zones to be welded 4 are coupled and melted together withoutdemounting the profiled elements 3 from the retaining members 2.

In other words, the tooling of the profiled elements 3 on the retainingmembers 2 occurs just once and the device 1 is able to execute all thesteps of the method according to the invention without the profiledelements 3 having to be prepared and/or machined on other machines.

Such perculiarity, besides ensuring very fast execution, permitsavoiding welding errors due to the incorrect mounting of the profiledelements 3 on the retaining members 2.

In fact, if the zones to be welded 4 were leveled on a different machineand then mounted on the device 1 to be welded, the risk would exist ofbadly welding the profiled elements 3 because the zones to be welded 4might not be perfectly facing and parallel.

With reference to the solution schematically shown in the FIGS. 7a and7b , the compartment 19 a previously made by the grooves 19 is open,meaning it has a side turned towards the outside which remainssubstantially accessible and visible.

In the solution shown in the FIGS. 7a and 7b , therefore, the weldingbead is retained within the volume of the compartment 19 a by means ofthe presser 27 which closes one of its sides.

It will be noted in fact that when the profiled elements 3 are movedcloser, the grooves 19 coincide with one another to define thecompartment 19 a. Furthermore, the presence of the presser 27 determinesthe closing of the compartment 19 a which keeps the welding bead on thesame level as the external visible surfaces of the profiled elements 3.

The step of making the groove 19 is implemented by means of a removaloperation of material on the peripheral edges defined by the headextremities of each profiled element 3. This way, the groove 19 obtainedhas a substantially stepped conformation in square, i.e., shaped at 90°,which extends along the entire extension of the zone to be welded 4.Before the step of heating the zones to be welded 4, and in particularduring the removal by milling step, the step is implemented of theretention of the shavings by means of the cutter tool 21 with helicalshape and the axial suction which conveys the removed shavings towardsthe inside of the chamber 29 a.

With reference to the solution shown in FIGS. 8a, 8b and 8c , thegrooves 19 made in correspondence to each zone to be welded 4 compriseat least an undercut portion 30 to define at least a protruding corner31 obtained on a visible surface portion 32 of the profiled elements 3.

Also in this case the step of making the grooves 19 is performed bymeans of a removal operation on a peripheral edge of each profiledelement 3, with the difference that a tool 21 is used which isspecifically shaped to make the undercut portion 30.

The tool 21, in particular, can be shaped so as to make the groove 19and its undercut portion 30 with a single material removal stroke directfrom the solid.

Alternative embodiments are however possible wherein the removaloperation is done by means of two different tools 21, one for shapingthe groove 19 in a way similar to that shown in the FIG. 7a , and onefor obtaining only the undercut portion 30.

The groove 19 thus obtained has a stepped conformation in undercut,which extends along the entire extension of the zone to be welded 4.

The undercut step is at least partially obtained underneath the visiblesurface portion 32 of the profiled elements 3 to define the undercutportion 30 of the groove 19.

More in detail, it is underlined that, once the grooves 19 have beenmade:

-   -   the zones to be welded 4 comprise a head surface 33 suitable for        coming into contact with the head surface 33 of the other zone        to be welded 4 during the coupling step of the profiled elements        3; and    -   the protruding corners 31 are arranged at a predefined distance        34 from the lying plane on which the head surfaces 33 lie.

The predefined distance 34 is determined according to the quantity ofplastic material to be melted during the coupling step of the profiledelements 3 and to the volume at disposal in the undercut portions 30 ofthe grooves 19 which, as will be better described below, is designed tocollect the melted material at the end of the coupling step of theprofiled elements 3.

Before the heating step, furthermore, the grooves 19 are delimited by afirst surface 35 substantially at right angles to the head surfaces 33and by a second surface 36 substantially oblique in correspondence towhich said undercut portion 30 is defined.

The second surface 36 is substantially sloped by an angle between 10°and 80° with respect to the visible surface portion 32 of the profiledelements 3.

Alternative embodiments of the present invention cannot however be ruledout wherein the grooves 19, and in particular the undercut portions 30thereof, have a different conformation, e.g., curved or the like.

In the light of the specific conformation of the grooves 19, during thestep of approach and coupling of the zones to be welded 4, the followingsub-steps are completed:

-   -   bringing the protruding corners 31 together so they        substantially coincide without substantially melting them; and    -   making a containing compartment 19 a which is defined by the        grooves 19 of each zone 4 and which, in correspondence to the        visible surface portion 32 of the profiled elements 3 is closed        by the protruding corners 31 brought close to one another.

In this configuration, therefore, the containing compartment 19 a isclosed and the welding bead is made inside the containing compartment 19a.

The plastic material melted in correspondence to the head surfaces 33does in fact return up towards the visible surface portion 32 of theprofiled elements 3 and remains trapped inside the containingcompartment 19 a.

In the case shown in the FIGS. 8a, 8b, 8c the containing pressers 27 areused resting on the profiled elements 3 in order to contain any leakingof the melted material through the protruding corners 31.

With reference to the solution shown in the FIGS. 9a, 9b, 9c and 9d ,the groove 19 is only obtained on one of the profiled elements to bewelded.

For this purpose, the profiled elements 3 can be split up into a firstprofiled element 3 a, on which the groove 19 is made, and into a secondprofiled element 3 b, on which, instead, the groove 19 is not obtained.

The step of making the groove 19 moulds the zone to be welded 4 of thefirst profiled element 3 a so as to define a head surface 40 and areceding corner 41 obtained on a visible surface portion 42 of the firstprofiled element 3 a.

Just as in the previous cases, in the solution shown in the FIGS. 9a,9b, 9c, 9d as well, the step of making the groove 19 is implemented bymeans of a removal operation on a peripheral edge of the first profiledelement 3 a.

After the step of making the groove 19, an operation is performedconsisting in the heating of the zones to be welded 4, which isperformed by bringing the profiled elements 3 a, 3 b closer to thehot-plate heat-sealing element 12.

During this step, a sub-step is carried out consisting in dissolving thehead surface 40 of the first profiled element 3 a and only a part of thezone to be welded 4 of the second profiled element 3 b, so as to definea receding surface 43 of the second profiled element 3 b and a reliefcorner 44 obtained on a visible surface portion 42 of the secondprofiled element 3 b.

For this purpose, in the solution shown in the FIGS. 9a, 9b, 9c and 9dthe hot-plate heat-sealing element 12 has a first face 45, suitable forcoming in contact with the head surface 40 of the first profiled element3 a, and a second face 46, 47 suitable for coming in contact with onlyone part of the zone to be welded 4 of the second profiled element 3 b.

More in detail, the second face 46, 47 comprises at least one protrudingpart 46, suitable for coming in contact with the second profiled element3 b to define the receding surface 43, and at least one receding part47, suitable for remaining spaced at a distance from the second profiledelement 3 b and for avoiding to come in contact with the relief corner44.

As can be seen in FIG. 9b , the second face 46, 47 has two recedingparts 47 which operate on opposite sides of the second profiled element3 b.

The distance h between the receding parts 47 depends on the height ofthe second profiled element 3 b; higher the second profiled element 3 b,greater the distance between the receding parts 47.

For this purpose, the hot-plate heat-sealing element 12 can be splitinto at least two sections 12 a, 12 b reciprocally mobile to move thereceding parts 47 close to and away from one another.

In the embodiment shown in the FIGS. 10a and 10b , e.g., each section 12a, 12 b is wedge-shaped and has a sloping surface 50 which can slide onthe sloping surface 50 of the other section 12 a, 12 b to change thedistance h between the receding parts 47.

Alternative equivalent solutions cannot however be ruled out such as,e.g., the case in which the second face 46, 47 consists of a kit ofinterchangeable sheets, shaped differently the one from the other (inparticular, they have different distances h) and selectively associablewith the hot-plate heat-sealing element 12 according to the height ofthe second profiled element 3 b.

After the heating step, a coupling step is performed of the zones to bewelded 4, which consists in reciprocally bringing the profiled elements3 a, 3 b closer along the sliding guides 8 and which contemplates thesub-step of melting the zones 4 together to define the above weldingbead.

In the light of the specific conformation of the receding corner 41, ofthe relief corner 44, of the head surface 40 and of the receding surface43, during the coupling step the following sub-steps are also performed:

-   -   melting the head surface 40 together with the receding surface        43; and    -   bringing the receding corner 41 close to the relief corner 44 so        they substantially coincide without substantially melting them,        to define a confinement barrier of the welding bead.

For this purpose is it underlined that, after the heating step andbefore the coupling step of the profiled elements 3 a, 3 b, the recedingcorner 41 of the first profiled element 3 a is arranged at a firstpredefined distance 48 from the lying plane on which the head surface 40of the first profiled element 3 a lies.

In the same way, after heating and before coupling, the relief corner 44of the second profiled element 3 b is arranged at a second predefineddistance 49 from the lying plane on which said receding surface 43 ofthe second profiled element 3 b lies.

Usefully, the first predefined distance 48 is greater or the same as thesecond predefined distance 49 and, preferably, it is slightly greater,so that at the time of the coupling of the profiled elements 3 a, 3 b,the head surface 40 and the receding surface 43 come into contact andmelt together, while the receding corner 41 and the relief corner 44simply rest against one another without melting.

The first predefined distance 48 and the second predefined distance 49are established according to the quantity of plastic material to bemelted during the coupling step of the profiled elements 3 a, 3 b.

In this configuration, therefore, the containing compartment 19 a inwhich the welding bead remains confined is defined by the spaceunderneath the confinement barrier.

It is in fact underlined that the plastic material melted incorrespondence to the head surface 40 and of the receding surface 43remains contained inside the containing barrier defined by the recedingcorner 41 and by the relief corner 44 and has no way of surfacingoutside the profiled elements 3 a, 3 b. In the case shown in the FIGS.9a, 9b, 9c the containing pressers 27 are used resting on the profiledelements 3 a, 3 b to curb any melted material leaking through thereceding corner 41 and the relief corner 44.

The adhesion capacity of the door or window frame in correspondence tothe welded extremities depends on the extension of the working surfacesof the profiled elements 3 which is placed in reciprocal contact andwhich, other sizings being equal, is determined by the thickness of thewall of the profiled elements 3.

The presence of the grooves 19 determines the reduction of the wallthickness of the profiled elements 3 and, other conditions being equal,the working surface to be melted and welded.

To ensure greater adhesion and increase the mechanical strength of theend door or window frames, the figures from 11 to 18 show an alternativeembodiment of the device or machine 1.

In this embodiment, the profiled elements worked by the machine 1 aresplit up into a first profiled element 60 and a second profiled element61, having a first zone to be welded 62 and a second zone to be welded63, respectively.

The machine 1 comprises a base frame 38, retaining members 2, movementmeans 7, removal means 18 and containing pressers 27 exactly the same asthose mentioned above, to the detailed description of which fullreference is made.

The hot-plate heat-sealing element 12 shown in the embodiment of thefigures from 11 to 18 has a first face 64 and a second face 65 oppositeone another against which the zones to be welded 62, 63 are placeable incontact to be heated.

Advantageously, the hot-plate heat-sealing element 12 consists of asingle resistance, with a substantially plate-shaped conformation andwhich, by means of an electric circuit 66, is supplied with electricityto produce heat by joule effect.

The first face 64 and the second face 65 are therefore defined by themain surfaces of the electric resistance 12.

It is easy to undertand however that alternatively the hot-plateheat-sealing element 12 can consist of a support plaque which, onopposite sides, supports two or more separate electrical resistances,one of which defines the first face 64 while the other defines thesecond face 65.

Alternatively, it is possibile to have a hot-plate heat-sealing element12 made up of one or more electric resistances with flat faces coveredwith a series of shaped elements, in a heating conductive material,which define the first face 64 and the second face 65; in this case, theshaped elements can usefully consist of a piece of metal plate subjectto bending, pressing or other type of shaping useful to shape the faces64, 65 in a way that will be better described below.

In a further alternative embodiment, it is possible for the hot-plateheat-sealing element 12 not to consist of an electric resistance but,rather, of one or more induction heating plates.

According to the present invention, the hot-plate heat-sealing element12 is shaped in such a way that:

-   -   the first face 64 comprise a plurality of first recesses 64 a        and of first protrusions 64 b alternated the one with the other        and suitable for making on the first zone to be welded 62 a        plurality of first reliefs 62 a and of first cavities 62 b        respectively;    -   the second face 65 comprises a plurality of second recesses 65 a        and of second protrusions 65 b alternated the one with the other        and suitable for making on the second zone to be welded 63 a        plurality of second reliefs 63 a and of second cavities 63 b        respectively.

The zones to be welded 62, 63, thus heated and shaped, can be joinedtogether with the first reliefs 62 a inserted in correspondence to thesecond cavities 63 b and with the second reliefs 63 a inserted incorrespondence to the first cavities 62 b.

As can be seen in FIG. 13, the first recesses 64 a are arranged on thehot-plate heat-sealing element 12 opposite the second protrusions 65 band the first protrusions 64 b are arranged opposite the second recesses65 a.

This means that where the first face 64 has a first recess 64 a, thesecond face 65 has a second protrusion 65 b, and where the first face 64has a first protrusion 64 b, the second face 65 has a second recess 65a.

Alternative embodiments cannot however be ruled out wherein the recesses64 a, 65 a of one face 64, 65 are not perfectly opposed to theprotrusions 64 b, 65 b of the other face 64, 65 and are more of lessstaggered with respect to these.

The first recesses 64 a are shaped substantially complementary to thesecond protrusions 65 b and, in the same way, the first protrusions 64 bare shaped substantially complementary to the second recesses 65 a.

Embodiments are also possible, however, wherein the recesses 64 a, 65 aand the protrusions 64 b, 65 b are not perfectly complementary.

In the embodiment shown in the illustrations, the recesses 64 a, 65 aand the protrusions 64 b, 65 b of the two faces 64, 65 extend alongrectilinear lines parallel to one another.

Usefully, the dimensions of the recesses 64 a, 65 a and protrusions 64b, 65 b made this way vary between 0.5 and 2 mm of thickness and between1 and 4 mm of depth and are preferably equal to about 1 mm of thicknessand 2 mm of depth.

Such sizing permits cutting the profiled elements 60, 61 in the best wayto obtain an intimate adhesion between the reliefs 62 a, 63 a and thecavities 62 b, 63 b during their joining and welding.

For reasons of clarity and simplicity of representation, theillustrations do not always show the real dimensions of the recesses 64a, 65 a, of the protrusions 64 b, 65 b, of the reliefs 62 a, 63 a and ofthe cavities 62 b, 63 b, which have sometimes been accentuated to permita greater understanding of the present invention.

In the embodiment shown in the illustrations, the rectilinear linesalong which the recesses 64 a, 65 a, of the protrusions 64 b, 65 bextend are substantially at right angles to the lying plane on which theprofiled elements 60, 61 lie and, in other words, are vertical.

It is however easy to understand that, alternatively, the aboverectilinear lines can be positioned parallel to the lying plane on whichthe profiled elements 60, 61 lie and therefore horizontally.

In another embodiment, instead, the rectilinear lines can be positionedoblique with respect to the lying plane on which the profiled elements60, 61 lie.

It cannot be ruled out that the recesses 64 a, 65 a and the protrusions64 b, 65 b have a different conformation with respect to the linear oneand, e.g., be substantially punctiform.

In this latter case, the protrusions 64 b, 65 b are defined by analternation of tapered cusps opposed to recesses 64 a, 65 a defined by aseries of cavities, these too tapered, cusps and cavities being arrangedin chequered fashion.

Usefully, the faces 64, 65 of the hot-plate heat-sealing element 12 arecovered with a non-slip material which prevents the plastic of theprofiled elements 60, 61 from adhering to the resistance 12 andremaining trapped inside the recesses 64 a, 65 a.

Such non-slip material, e.g., consists of teflon, ceramics, or teflonspray.

For any event, however, the machine 1 also comprises cleaning means 67associated with the base frame 38 and suitable for removing any portionof plastic which has remained attached to the hot-plate heat-sealingelement 12.

The cleaning means 67 are composed, e.g., of a pair of brushes suitablefor passing over the first face 64 and over the second face 65respectively.

The FIGS. 11 and 12 only show the brush 67 intended to clean the secondface 65, but it is easy to appreciate that an identical brush 67 isprovided to clean the first face 64.

The brushes 67 are fitted on the base frame 38 of the machine 1 in afixed way and on opposite sides with respect to the movement path of thehot-plate heat-sealing element 12.

This way, the brushes 67 have the chance to pass over the faces 64, 65during the transit of the hot-plate heat-sealing element 12 between theactive condition and the non-use condition operated by the movementsystem 13.

Alternative embodiments cannot however be ruled out wherein the brushes67 have a mobility such as to make the cleaning operation of the faces64, 65 easier.

Consistently with the embodiment of the machine 1 shown in the figuresfrom 11 to 18, the method or procedure according to the presentinvention contemplates heating the zones to be welded 62, 63 moving themcloser together and placing them in contact with the faces 64, 65 of thehot-plate heat-sealing element 12 (FIGS. 15 and 16).

The conformation of the faces 64, 65 results in the first reliefs 62 aand the first cavities 62 b being made on the first zone to be welded 62and in the second reliefs 63 a and the second cavities 63 b being madeon the second zone to be welded 63 (FIG. 17).

At this point, the heated zones to be welded 62, 63 are coupled togetherby pressing, with adequate pressure, the profiled elements one againstthe other to keep the zones to be welded 62, 63 in reciprocal contact.

This step of the procedure occurs taking care to arrange the firstreliefs 62 a in correspondence to the second cavities 63 b and thesecond reliefs 63 a in correspondence to the first cavities 62 b.

Subsequently, the faces 64, 65 of the hot-plate heat-sealing element 12are cleaned so as to remove any portions of plastic which have remainedattached to the hot-plate heat-sealing element 12.

This part of the procedure is performed by passing the brushes 67 overthe first face 64 and the second face 65 respectively during themovement of the hot-plate heat-sealing element 12 between the activecondition and the non-use condition.

The present invention achieves the proposed objects. In particular, thepossibility of maintaining the welding bead inside the compartment 19 aand the operation of the containing pressers 27 prevents excess materialcoming out. Consequently, all the surface finishing jobs suitable forremoving excess material are eliminated, with the consequent advantagesin terms of time, energy and saving relating to the use of furthermachinery.

Furthermore, the removal operation ensures the leveling of the surfacesof the profiled elements 3 in reciprocal contact, with the consequentsaving of the material which, at present, has to be melted to obtain therequired amount.

It is further underlined that the particular solution of providingrecesses and protrusions on the welding plate and of making reliefs andcavities on the zones to be welded permits considerably increasing thestrength and mechanical tightness of the welding.

The reciprocal coupling of the reliefs and cavities in the waysindicated by the present invention does in fact determine the intimateadhesion of the zones to be welded by virtue of the fact that thecontact surface is greater compared to a traditional coupling betweenperfectly flat zones to be welded.

It must also be underlined that the moving away of the welding plate andthe surface tension of the melted material usually determine theformation of a thin surface repellent layer, so-called “skin”, which atleast in part hinders the subsequent adhesion of the extremities of theprofiled elements; the presence of reliefs and cavities, alternated theone with the other, on the other hand, strongly hinders the formation ofthe “skin” surface layer, which tends to only form in the most exposedparts of the reliefs, without affecting the cavities.

For all these reasons, we witness an increase in the adhesion capacitybetween the two head extremities of the profiled elements which permitsachieving a roughly 30% improvement in ultimate strength.

In this respect, a series of laboratory tests have been performed onseveral pairs of test profiled elements of the same shape and size andwhich, other conditions being equal, only differ in terms of thefollowing characteristics:

A) non-milled test profiled elements, i.e., without grooves 19, andtraditionally welded, i.e., by means of a welding plate without recesses64 a, 65 a and protrusions 64 b, 65 b;

B) non-milled test profiled elements but welded according to theinvention, i.e., by means of a welding plate with the recesses 64 a, 65a and the protrusions 64 b, 65 b;

C) milled test profiled elements, i.e., having grooves 19, buttraditionally welded;

D) test profiled elements milled and welded according to the invention.

By way of example, by indicating as 1 kg the ultimate strength value forcase A) and comparing such reference value with the data acquired forthe cases B), C) and D), the following results are obtained:

-   ultimate strength of case A): 1 kg-   ultimate strength of case B): 1.3 kg-   ultimate strength of case C): 0.83 kg-   ultimate strength of case D): 1.1 kg

As can be seen from the obtained data, therefore, it appears evidentthat the use of a welding plate with recesses 64 a, 65 a and protrusions64 b, 65 b permits strengthening the connection between the profiledelements both when there are no grooves 19 (switch from 1 kg to 1.3 kg)and when there are grooves (switch from 0.83 kg to 1.1 kg).

It is also underlined that, compared to a traditional welding, theadoption of the grooves 19 intended to create a containing compartmentfor the welding bead determines a considerable reduction in strength(switch from 1 kg to 0.83 kg) due to the reduction in thickness of thewall of the profiled elements but, by means of the present invention,the strength limit can be returned to values above initial values(switch from 0.83 kg to 1.1 kg).

The particular solution of combining the removal means 18 and thewelding plate 12 with recesses 64 a, 65 a and protrusions 64 b, 65 b ona single welding machine, therefore permits obtaining a result neverbefore achieved to make window and door frames in a plastic material ofconsiderable sturdiness and with an appreciable aesthetic appearance,which do not require additional finishing operations.

1.) A method for welding profiled elements in plastic material, inparticular PVC, comprising the steps of: preparing at least two profiledelements (3; 3 a, 3 b; 60, 61), arranged with respective zones to bewelded (4; 62, 63) facing one another; making a groove (19) incorrespondence to at least one zone to be welded (4; 62, 63) of theprofiled elements (3; 3 a, 3 b; 60, 61), said step of making the groove(19) being performed by means of a removal operation on a peripheraledge of at least one profiled element (3; 3 a, 3 b; 60, 61); heatingsaid zones to be welded (4; 62, 63); coupling the zones to be welded (4;62, 63) to one another, pressing the profiled elements (3; 3 a, 3 b; 60,61) one against the other so as to keep the zones to be welded (4; 62,63) in reciprocal contact; said step of coupling the zones to be welded(4; 62, 63) comprising a sub-step of melting the zones to be welded (4;62, 63) into one another in order to define a welding bead and asub-step of making a containing compartment (19 a) defined by said atleast one groove (19); said welding bead being made internally of saidcontaining compartment (19 a); wherein said step of coupling the zonesto be welded (4; 62, 63) comprises the step of arranging a containingpresser (27) in correspondence to said containing compartment (19 a) forpreventing exit of the welding bead from the compartment itself. 2.)Method according to claim 1, wherein said removal creates a step of saidperipheral edge, developing along the whole development of the zone tobe welded (4; 62, 63) of said profiled element (3; 3 a, 3 b; 60, 61).3.) Method according to claim 1, wherein said step of making a groove(19) is performed in correspondence to each zone to be welded (4; 62,63) and said step of making a containing compartment (19 a) is performedby abutting the zones to be welded (4; 62, 63) against one another; saidcompartment (19 a) being defined by said grooves (19) in reciprocalcollaboration on a visible surface portion of said profiled elements (3;3 a, 3 b; 60, 61).
 4. Method according to claim 3, further comprisingthe step of arranging a pair of said pressers (27), facing one another,and both mobile in a reciprocal moving close direction incorrrespondence to a respective compartment (19 a). 5.) Method accordingto claim 1, further comprising the sub-step of retaining the shavingsobtained during the removal operation by means of an electrostaticfield.) 6.) Method according to claim 1, further comprising the sub-stepof suctioning the shavings obtained during the removal operation. 7.)Method according to claim 1, wherein said step of making a groove (19)comprises leveling the parts of said zones to be welded (4; 62, 63) notoccupied by said groove (19). 8.) Method according to claim 1, whereinsaid groove (19) comprises at least an undercut portion (30) to defineat least a protruding corner (31) obtained on a visible surface portion(32) of said profiled elements (3); said step of coupling the zones tobe welded (4) comprising the sub-step of bringing said protrudingcorners (31) together so they substantially coincide withoutsubstantially melting them, in correspondence to the visible surfaceportion (32) of said profiled elements (3), said containing compartment(19 a) being closed by said protruding corners (31) brought close to oneanother. 9.) Method according to claim 8, wherin said step is at leastpartially obtained underneath the visible surface portion (32) of saidprofiled elements (3) to define said undercut portion (30). 10.) Methodaccording to claim 8 , wherein, before said heating step, said zones tobe welded (4) comprise a head surface (33) suitable for coming intocontact with the head surface (33) of the other zone to be welded (4)during said coupling step, said protruding corners (31) being arrangedat a predefined distance (34) from the lying plane on which said headsurfaces (33) lie, said predefined distance (34) being determinedaccording to the quantity of plastic material to be melted during saidcoupling step. 11.) Method according to claim 10, wherein, before saidheating step, said grooves (19) are delimited by a first surface (35)substantially at right angles to said head surfaces (33) and by a secondsurface (36) substantially oblique in correspondence to which saidundercut portion (30) is defined, said second surface (36) beingsubstantially sloped by an angle between 10° and 80° with respect tosaid visible surface portion (32) of said profiled elements (3). 12.)Method according to claim 1, wherein: said profiled elements (3; 3 a, 3b; 60, 61) comprise a first profiled element (60) and a second profiledelement (61), having a first and a second zone to be welded (62, 63),respectively; said heating comprises heating said zones to be welded(62, 63) by means of at least one hot-plate heat-sealing element (12),having a first face (64) and a second face (65) oppposite one another onwhich said zones to be welded (62, 63) can be placed in contact, whereinsaid heating comprises the steps of: making on said first zone to bewelded (62) a plurality of first reliefs (62 a) and of first cavities(62 b) by means of a plurality of first recesses (64 a) and of firstprotrusions (64 b) arranged on said first face (64); and making on saidsecond zone to be welded (63) a plurality of second reliefs (63 a) andof second cavities (63 b) by means of a plurality of second recesses (65a) and of second protrusions (65 b) arranged on said second face (65);said coupling occurs with said first reliefs (62 a) in correspondence tosaid second cavities (63 b) and with said second reliefs (63 a) incorrespondence to said first cavities (62 b). 13.) Method according toclaim 12, further comprising the step of cleaning said faces (64, 65)which is suitable for removing any portion of plastic which has remainedattached to said hot-plate heat-sealing element (12). 14.) Methodaccording to claim 13, wherein said cleaning comprises having a pair ofbrushes (67) passing over said first face (64) and over said second face(65), respectively. 15.) Method according to claim 14, furthercomprising the step of moving said hot- plate heat-sealing element (12)between a working configuration, wherein it is placed between saidprofiled elements (60, 61), and an idle configuration, wherein it ismoved away from said profiled elements (60, 61), said passing overoccurring during the transit of said hot-plate heat-sealing element (12)between said active condition and said non-use condition. 16.) Methodaccording to claim 2, wherein said step of making a groove (19) isperformed in correspondence to each zone to be welded (4; 62, 63) andsaid step of making a containing compartment (19 a) is performed byabutting the zones to be welded (4; 62, 63) against one another; saidcompartment (19 a) being defined by said grooves (19) in reciprocalcollaboration on a visible surface portion of said profiled elements (3;3 a, 3 b; 60, 61). 17.) Method according to claim 2, further comprisingthe sub-step of retaining the shavings obtained during the removaloperation by means of an electrostatic field. 18.) Method according toclaim 3, further comprising the sub-step of retaining the shavingsobtained during the removal operation by means of an electrostaticfield. 19.) Method according to claim 4, further comprising the sub-stepof retaining the shavings obtained during the removal operation by meansof an electrostatic field. 20.) Method according to claim 2, furthercomprising the sub-step of suctioning the shavings obtained during theremoval operation.